This invention pertains to means for providing therapeutic silver ions and is more particularly concerned with a direct current source for releasing silver ions from an anodal electrode.
The bactericidal action of ionic silver has been known for years. It has been found that silver ions, when applied to tissue, will kill a broad spectrum of bacteria and other microorganisms. One source of silver ions is dissociable silver compounds which are topically applied to infected tissue.
A more effective ion source than silver compounds is a silver bearing electrode in close proximity to the tissue undergoing treatment. Usually the silver bearing electrode is positive in a direct current circuit. A return electrode, in contact with another area of the patient, provides a return path completing the circuit.
Direct current liberates ionic silver from the anodal electrode. The silver ions penetrate the infected tissue and bactericidal contaminants to a depth of about one centimeter. Because of the limited penetration the infected area is usually debrided prior to treatment.
Only small levels of direct current are needed. One worker, R. O. Becker, has found 300 MA satisfactory for treatment of chronic osteomyelitis. Current was supplied by a constant current generator.
The electrical resistance of both the tissue being treated and the tissue-electrode interface is a resistive load to the D.C. generator. In accordance with Ohm's law, inter-electrode voltage will increase with resistance if a constant current generator is used. At high resistance the voltage may exceed 1.1 volts whereupon half-cell electrolysis occurs and tissue is destroyed.
It is therefore an object of the invention to provide a direct current source for ionic therapy which provides a constant level of direct current under most normal load conditions while avoiding electrode voltages sufficient to cause electrolysis.
Another object is to provide a direct current source for ionic therapy having as two load-dependent modes constant current and constant voltage.